Spirometry is probably the most known and most widely used lung function test and an important examination method in pneumology. The lungs are well-examinable by imaging methods such as chest X-ray or computed tomography, but these examinations "only" show the anatomical structure of these organs and do no say anything about actual lung functions.
The examination procedure is performed with a device known as the spirometer. There are several types of these instruments, but in principle, it is always a tube-shaped device with a mouthpiece, which the patient places in his mouth. The nose is clogged by a special pin and the patient breathes by mouth into the instrument. After a while, when breathing normally, the patient is asked by the examiner to take a deep breath with maximum exhalation and also inhalation followed by the fastest possible maximal exhalation. The detected values are processed by the device and the result is a number of "breathing curves". These curves are essential for evaluation of lung functions and decoding the type and severity of the present disorder.
The testing is sometimes performed in patient with a lung disease who are examined before- and after taking their bronchodilating medication to assess the therapeutic effect on lung functions.
The examination does not need any special preparation, but it is advisable to avoid smoking about 6 hours before the procedure.
The examination can help to diagnose functional disorders of the lungs and determine their severity. The test may be used to distinguish very common COPD from asthma. It also allows to evaluate pulmonary function in pulmonary fibrosis, cystic fibrosis and in patients with lung cancer before surgery to evaluate the possibility of resection of a part of the affected lungs. Spirometric examination may be beneficial in unexplained shortness of breath, where the cardiac etiology is unlikely.
The examination does not have any clinically important disadvantages, but sometimes, it must be complemented by more complex function lung tests. A certain disadvantage is the fact that the correct recording needs an active cooperation of the patient, which can be sometimes somehow problematic (in children, in people with disorders of consciousness, in mentally-ill patients, etc.).